A new NaI gamma-ray spectrometer

Abstract An improved NaI gamma-ray spectrometer has been developed for the detection of 10–40 MeV gamma rays. It consists of a 25.4 cm diameter × 25.4 cm long NaI cylinder surrounded by a plastic scintillator anticoincidence shield which is 10.8 cm thick. An energy resolution of 3.2% fwhm has been achieved for 15 MeV gamma rays. It has also been observed that the uniformity of pulse-height response in large plastic scintillators with polished surfaces is far superior to that of scintillators with surfaces which are painted white.